This invention relates generally to the art of packaging and more particularly to the art of packaging with flexible transparent film which self-adheres during the packaging process.
Articles such as food stuffs, clothing and the like have been commonly packaged in flexible plastic bags or containers which are impervious to the passage of air and other deleterious gasses as well as liquids and moisture.
Packaging processes utilizing a laminate of a self-adhering plastic material and a structural layer of a copolymer of vinylidene chloride and vinyl chloride (saran) is described in U.S. Pat. No. 3,625,348. By the process described therein, a container formed of this laminate material is utilized for packaging such that the self-adhering layer faces an article to be packaged and adheres to itself and conforms to the article shape during a heating step at a relatively low temperature. A preferred embodiment of this patent utilizes an oriented layer of saran with a self-adhering layer of a copolymer of ethylene and vinyl acetate. In this embodiment a packaged article may be placed within a container of this laminate with the self-adhering layer facing the article as well as itself. By evacuating the container and immersing the thus filled container within water maintained at a temperature near the boiling point thereof, the self-adhering layer adheres tightly to itself while at the same time, the oriented saran layer shrinks to provide a tightly packaged article surrounded by an adherent material. The saran layer in such a structure provides strength and shrinkability to the overall structure while the copolymer of ethylene and vinyl acetate self-adheres to provide protection from the ingress of deleterious substances should a puncture occur.
While packages composed of the film described in the above referenced patent are highly satisfactory for many applications, there are shortcomings of the prior art structure which the art heretofore has neither recognized nor eliminated.